1. Field of the Invention
The present invention relates to a conveying roller for photosensitive material, and a method of producing the same. More particularly, the present invention relates to a conveying roller for photosensitive material, which has high resistance to abrasion and can be produced easily, and a method of producing the same.
2. Description of the Related Art
Photosensitive material, in general, is constituted by a support and a photosensitive layer of photographic emulsion, which is applied as a coating to, or deposited to, the support. According to various kinds of the support, there are plural examples of photosensitive material, including photo film, dry plate, and photographic paper. The photo film has the support produced from film of resin. Types of the photo film includes a roll photo film and a sheet photo film. Examples of the roll photo film include the 8 mm type and the 1,000 mm type. Examples of the sheet photo film include types of 4×5 cm, the cabinet size (halfplate), B5, A4, B4, A3 and 10×12 inches. As a form of the most widely used photo film, a photo film cassette is well-known, and includes a cassette shell, a spool rotatable inside the cassette shell, and a strip of the photo film whose end is retained on the spool and which is wound about the spool.
The photo film is conveyed by conveying rollers in optical instruments. Conveying rollers for use in the photo film manufacturing apparatus, a photographic printer and a photo film processor are constituted by a roller body formed by cutting and scraping a rod of stainless steel, or by a roller body of metal and hard chromium plating formed on its surfaces. To avoid damaging continuous photo film and photo filmstrip in conveyance, a surface of the roller is finished by polishing, and smoothed for the contact with the photo film.
There is a type of photo filmstrip including a magnetic recording layer, which is a coating of magnetic material applied to the support on the side opposite to the photosensitive layer, so that the photo filmstrip can operate for storing magnetic information written thereto. There is abrasive material or polishing agent, mixed with the magnetic material, for contacting a magnetic head of an information reader/writer, to remove dust or dirt from the magnetic head. When a conveying roller contacts the continuous photo film which will become this type of photo filmstrip, the conveying roller is abraded and deformed by the abrasive material of the photo film, because the conveying roller contacts the magnetic recording layer. It is likely that the continuous photo film or photo filmstrip is fogged by pressure, scratched or damaged. A life of the roller is short, so that each roller must be replaced with an unused one very frequently.
To solve those problems, JP-A 8-262680 (corresponding to U.S. Pat. No. 5,520,601) discloses a use of such ceramics for a conveying roller as yttria-alloyed tetragonal polycrystalline zirconia, which is zirconium oxide and yttria mixed therewith at 3-5 mole %. Ceramics characteristically have a higher hardness than stainless steel and hard chromium plating, and have higher resistance to abrasion. However it is difficult to cut or scrape a ceramic product into a complicated shape due to the considerable hardness of the ceramics. Ceramics are unsuitable for shaping the roller which includes a roller core and flanges on respective ends of the roller core, and in which a diameter of the roller core is partially changed. Moreover a problem lies in that zirconia stabilized by use of yttria is likely to collect static charge electrically. The continuous photo film might be fogged and have a lowered quality.
A guide rail 120 according to the related art is described with reference to FIG. 9. The guide rail 120 consists of a combination of an upper guide plate 121 and a lower guide plate 122 secured thereto. The guide plates 121 and 122 are extended in a conveying direction of the continuous photo film 11, and define a photo film conveying path 123 between them for passing the continuous photo film 11. Respective lateral edges of the photo film conveying path 123 have support grooves 124 and 125, which are formed to reduce a range of the photo film conveying path 123 in its thickness direction. Support surfaces of the support grooves 124 and 125 support lateral edges of the continuous photo film 11. Lateral surfaces of the support grooves 124 and 125 prevent the continuous photo film 11 from being offset in the width direction. An area of contact between the continuous photo film 11 and the inside of the photo film conveying path 123 is reduced by the operation of the support grooves 124 and 125. The photo film surface of the continuous photo film 11 is prevented from being damaged while the continuous photo film 11 is conveyed. Inner corners 124a, 124b, 124c, 125a, 125b and 125c are defined on the support grooves 124 and 125, and rounded with a curvature, so as to reduce load to the continuous photo film 11 contacted by the support grooves 124 and 125. The guide rail used in the photo film manufacturing apparatus, or optical instruments such as photographic printer, photo film processor and others for use with photo film, is constituted by the upper and lower guide plates produced by cutting and scraping a stainless steel plate. Moreover hard chromium plating is formed on surfaces of the scraped plate before assembly of the guide rail. To avoid damaging the continuous photo film or photo filmstrip being conveyed, the guide rail is finished by the polishing finish or sanding finish to have a smoothed contact surface.
However there is a problem in the guide-rail according to the related art in that precision in regulating the continuous photo film in the width direction is likely to become low. This is because lateral walls of the conveying path are likely to be ground and deformed by contact with the edges of the continuous photo film, typically when used in the apparatus where the continuous photo film is conveyed at high speed. To maintain high precision in the positions, the guide rails must be renewed in a considerably frequent manner. The cost for the manufacturing apparatus is thus high.
To solve those problems, JP-A 8-310698 discloses a guide rail in which a protective member is attached to the inside surface of the conveying path, and a use of such ceramics for the protective member as yttria-alloyed tetragonal zirconia polycrystals (YTZP), which is zirconium oxide and yttria mixed therewith at 3-5 mole %. As ceramics have higher hardness and higher resistance to abrasion than stainless steel or hard chrome plating which is used conventionally, the attached ceramic protective member raises the surface hardness inside the conveying path. It is however extremely difficult to cut and scrape a complicated shape of a ceramic member, because of the hardness of the ceramic. The guide rail 120 of FIG. 9, in which the corners are defined on the support grooves 124 and 125, and rounded with a curvature, is so complicated that a protective member associated therewith is difficult to produce. The zirconia stabilized with yttria is likely to be charged electrically. Pressure fogging and scratches are likely to occur, which would damage the image quality of the continuous photo film 11.
The photo filmstrip may include a magnetic recording layer. When the conveying path of the guide rail contacts the continuous photo film, which will become this type of photo filmstrip, the conveying path is abraded and deformed by the abrasive material in the magnetic recording layer, because the conveying path contacts the magnetic recording layer. It is likely that the continuous photo film or photo filmstrip is fogged by pressure, scratched or damaged.